Some telephone receivers have high acoustic impedance, wherein the quality of the receiver's audio frequency response and the loudness decreases substantially with increasing sound leakage between the user's ear and the receiver ear cup. Many high acoustic impedance telephone receivers thus locate the speaker sound ports in a depression or in a cup that provides an effective seal with the user's ear. The development of increasingly smaller communications handsets has correspondingly reduced the receiver earpiece size, particularly on wireless communications handsets, which has made it increasingly difficult to provide an effective the earpiece seal required of high impedance acoustic impedance receivers.
Telephone receivers having low acoustic impedance are also known. In low acoustic impedance receivers, the quality of the receivers audio frequency response and the loudness is less dependent upon the seal between the earpiece and the user's ear, and thus these receivers tolerate some audio leakage. Leak-tolerant earpiece designs provide improved audio quality, but generally require additional parts and engineering.
In many communications handsets, the receiver earpiece is a single sound port, which is susceptible to blockage by soft ear tissue, resulting potentially in a substantial degradation of audio performance. The tendency to block the sound port is particularly problematic in smaller handsets, but is apparent nevertheless in larger handsets.
Prior art FIG. 5 illustrates a recess 50 on an outer surface of a receiver earpiece within which is located a sound port 60. The recess reduces some blockage of the sound port, but this recessed structure remains susceptible to blockage by the user's ear tissue.
The various aspects, features and advantages of the present disclosure will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description with the accompanying drawings described below.